Conventionally, an air-mixing type air conditioner, which adjusts the ratio between cold air and hot air to adjust the temperature of air blown into a room, is a typical air conditioner for a vehicle. FIG. 15 shows a conventional structure of this air-mixing type air conditioner and shows a right-and-left independent control type air conditioner in which an air passage in a case 21 is partitioned into a right air passage 26a and a left air passage 26b by a partition plate 25 and in which the temperatures of air to be blown into the right and left air passages are independently controlled.
Specifically, cold air bypass passages 29a, 29b are formed on both of the right and left sides of a heating heat exchanger 24. Furthermore, the ratio between cold air passing through these cold air bypass passages 29a, 29b and hot air passing through the right and left heat exchange portions of the heating heat exchanger 24 is adjusted by right and left air mixing doors 31, 32 to independently control the temperature of air blown into the right and left zones in a vehicle compartment.
On the other hand, U.S. Pat. No. 5,062,473 proposes an air mix type air conditioner in which: an opening for passing air is formed in a center area of a heat exchanger for heating air (heater core); a heating part for heating air by using hot water (engine cooling water) as a heat source is set on both sides of the opening in the center area; and the open ratio between the opening in the center area and the heating parts set on both sides is adjusted by two air mixing doors (i.e., sliding doors).
In the conventional structure shown in FIG. 15, a cold air flow A and a hot air flow B are formed singly in the respective right and left air passages 26a, 26b partitioned by the partition plate 25. These cold air flow A and hot air flow B flow are made in parallel toward an air blowoff opening (air outlet opening), for example, face opening parts 35a, 35b on a downstream side of the heating heat exchanger 24.
As a result, when a distance L1 from the heating heat exchanger 24 to the air blowoff openings (face opening parts 35a, 35b) is short, cold air and hot air are blown into the vehicle compartment before they are not sufficiently mixed with each other, thereby causing a problem that variations in the temperature of air blown into the vehicle compartment are large. To overcome this problem, an air guide for making cold air collide with hot air to mix them sufficiently may be provided on the downstream side of the air flow of the heating heat exchanger. However, in this case, the installation of the air guide will increase a pressure loss of the air flow.
By contrast, in U.S. Pat. No. 5,062,473, cold air passes through the opening in the center area of the heat exchanger for heating air and hot air passes on both sides of the cold air flow in the center area and hence the contact parts of the cold air and the hot air are formed on both sides of the opening in the center area. However, even in U.S. Pat. No. 5,062,473, when the above-described distance L1 is short, the cold air is not sufficiently mixed with the hot air, which results in increasing variations in the temperature of air blown into the vehicle compartment.